The present invention is directed to an expansion anchor assembly made up of an expansion sleeve, an expansion body and an anchor rod secured to the expansion body so that the rod serves for the attachment of a load to the assembly and also axially displaces the expansion body through the sleeve for displacing at least a part of the sleeve radially outwardly into anchoring engagement with the surface of a borehole into which the assembly is inserted.
Known expansion anchor assemblies are secured in a borehole by pulling a generally conically shaped expansion body in the direction out of the borehole. The pulling action is provided by anchor rods secured to the expansion body. In the expanding or spreading of the expansion sleeve, the expansion body moves along the inside surface of the sleeve and presses the sleeve radially outwardly into anchoring engagement with the surfaces of the borehole. As the expansion body is drawn into the expansion sleeve, at least an axially extending portion of the sleeve is deformed because of the changing diameter, that is, the sleeve is expanded or spread due to the conical shape of the expansion body. As the expansion body is drawn into the sleeve the surface of the sleeve may become jammed on the expansion body so that a displacement of the expansion sleeve together with the expansion body without obtaining anchoring values may take place. The radial displacement of the expansion sleeve during the anchoring process also produces a very high tensile stress in the anchor rod. Another considerable disadvantage when such jamming action occurs is that after spreading of the anchoring assembly is, in most instances, not attainable.